This is a P41 renewal proposal to continue the National Biomedical Center for Advanced ESR Technology (ACERT). Three principal areas of Core Research will be emphasized. They consist of Pulsed and Two-Dimensional Fourier Transform ESR;High Frequency-High Field (HFHF) ESR;ESR Microscopy. The first area includes two specific projects: Protein Structure Determination by Pulse ESR;also Membrane and Protein Molecular Dynamics and Protein Folding Dynamics by 2D-FT-ESR. The second area includes two specific projects: Multifrequency Studies of Dynamics in Proteins and Membranes and HFHF Instrumentation Development;also Development of High Power Pulsed HFHF ESR for Studies of Dynamics and Structure of Membranes and Proteins. The last area is one project: ESR Microscopy. Extensive collaborations with biomedical researchers will greatly benefit from these Core Projects, which in turn are driven by the collaborative needs for the new and improved technologies. Thus, there is an important synergism amongst the Core Projects and Collaborations. The technologies being developed at ACERT are in many respects unique in the world. The extensive collaborative and service projects at ACERT will continue to bring these modern ESR methods to the forefront of biomedical research, especially as the additional challenges are addressed in the Core Research Projects. This includes our plans to increase throughput of our facilities for which there are growing collaborative and service demands. The plans for service, dissemination and training address the need to bring these new technologies to other laboratories in the USA and elsewhere in addition to making the facilities available to outside scientists, publishing and advertising the results of the Center and running workshops on the new methodologies.